1. The Field of the Invention
The present invention relates to insulative connectors used to secure together layers of insulating and structural materials within a composite wall structure. In particular, the present invention relates to connectors and brackets for securing together an insulating layer and two structural layers made of a hardenable material and for securing a reinforcement material in position before the structural layers are formed and hardened.
2. Relevant Technology
As new materials and compositions have been developed, apparently unrelated materials have been synergistically combined to form useful composite materials. One such example is seen in the area of building and construction, in which high strength structural walls have been coated and layered with highly insulative materials which generally have relatively low structural strength. The resulting composite wall structure has high strength and is highly insulative. Conventionally, the structural component of such as a wall is built first, after which the insulating layer or sheet is attached to the structural component. Thereafter a protective cover is placed over the insulating material to protect and hide it. The insulating barrier reduces the transfer of thermal energy across the composite wall structure.
Concrete is one of the least expensive and strongest materials commonly used in the construction industry. Unfortunately, concrete, which is a mixture of hydraulic cement, water, and an aggregate such as rocks, pebbles, and sand, offers relatively poor insulation compared to many other materials. For example, a slab of concrete having an 8 inch thickness has an R value of about 0.64, while a one-inch thick panel of polystyrene has an R value of about 5.0. The R value of a material is proportional to the thermal resistance of the material and is useful for comparing the insulating properties of materials used in the construction industry.
In contrast with concrete, highly insulative materials, at least those of reasonable cost, typically offer poor structural strength and integrity. While lightweight aggregates having higher insulating ability may be incorporated within concrete to increase the insulating effect thereof, the use of such aggregates in an amount that has a dramatic effect on the insulation ability of the concrete will usually result in greatly decreased strength of the resulting structure.
It has been found that positioning at least one concrete layer adjacent to at least one insulating layer provides a composite structure that has both good insulating capability and good structural strength. One strategy for forming these composite wall structures is to position an insulating layer between two concrete layers. This technique, however, poses the risk of allowing the two concrete layers to collapse together or to separate apart during construction or subsequent use of the building. Accordingly, it is typically necessary to structurally bridge or connect the two concrete layers together. This is conventionally accomplished by using metal studs, bolts, or beams.
Because metal readily conducts thermal energy, metal studs, bolts and beams that are used to structurally bridge a pair of structural layers have the effect of significantly reducing the insulating properties of a composite wall. In particular, such metal studs, bolts, or beams provide channels through which thermal energy may be conducted. This is true even though the metal members may be surrounded by ample amounts of insulating material. Composite wall structures that use metal connecting members do not prevent heat from flowing from a relatively warm inside wall to a colder outside wall during cold weather, for example, as effectively as composite walls that do not use metal connecting members. Of course one might construct a building having no structural bridges between the inner and outer structural walls, although the result would be a building having inadequate stability for most needs.
In order to reduce thermal bridging, some have employed connector rods having a metal portion that passes through the concrete layers and a thermally insulating portion that passes through the insulating layer, e.g., U.S. Pat. No. 4,545,163 to Asselin. Others have developed connector rods made entirely from polymeric or other highly insulative materials. Examples of the foregoing include U.S. Pat. No. 4,829,733 to Long; U.S. Pat. No. 5,519,973 to Keith et al.; U.S. Pat. No. 5,606,832 to Keith et al.; and U.S. Pat. No. 5,673,525 to Keith et al. For purposes of disclosure, the foregoing patents are incorporated herein by specific reference.
In order to use a highly insulating connector to form a composite wall structure, the connector must be inserted through the insulating layer such that there is an end of the connector in each of the two structural layers. One method of inserting a connector through an insulating layer involves pre-drilling a set of holes in the positions where the connectors are to be situated. Of course, this involves an additional construction or manufacturing step, thereby increasing the amount of time needed and the overall cost of the finished product. In order to reduce the need for pre-drilled holes or to eliminate them altogether, there have been developed connector rods having a substantially pointed tip that is used to penetrate through the insulating layer. When inserting a connector rod through an insulating layer, it is desirable to reduce the amount of crushing, shearing, and other deformation of the insulating layer and to encourage the insulating layer to tightly conform to the connector rod. Otherwise, unhardened concrete may backflow around the connector rod and through the insulating layer to form a thermal bridge that reduces the insulating effectiveness of the composite wall structure.
It is well known in the construction industry that the structural properties of concrete are enhanced by embedding or otherwise positioning reinforcement materials therein. Concrete has very high compressive strength but offers relatively low tensile strength. For this reason, it is common to include high tensile strength reinforcement materials in concrete structures. The resulting reinforced concrete combines the high compressive strength of the concrete with the high tensile strength of the reinforcement materials. Such reinforcement materials typically include rebar, metal cables, wires, natural and synthetic organic fibers, metal fibers, wire mesh, and the like.
There are several ways in which composite wall structures having concrete layers may be formed. A first method involves successively forming or positioning the concrete and insulating layers in a horizontal orientation, allowing the concrete to cure, and tilting the resulting composite wall structure to a vertical position using a crane or other lifting mechanism. The need for moving the pre-formed composite wall structure can be eliminated, however, by forming the concrete layers vertically and in-place. Once such technique involves first positioning an insulating layer in an upright position. The insulating layer may have connector rods already inserted therethrough or the connector rods may be positioned at this point. A pair of temporary forms or molding structures are positioned on either side of the insulating layer. The concrete layers may then be formed on either side of the insulating layer using the forms to give the concrete layer the desired shape.
As mentioned previously, it is often desirable to include a reinforcement material in the concrete layers. However, it has proved difficult to adequately position reinforcement material in a fixed and ordered arrangement in preparation for the vertical and in-place formation of concrete panels. Reinforcement materials often do not have the stiffness and structural integrity to support themselves within the spaces between the insulating layer and the forms. Some reinforcement materials such as rebar can support themselves, although it is difficult to arrange rebar or other similar materials in an orderly and uniform fashion in preparation for pouring concrete layers in place.
In view of the foregoing, there exists a need for connectors that have the ability to secure reinforcement materials in place and in a fixed position prior to the formation and curing of a concrete structural layer.
It would be another advancement in the art if such connectors could also be molded in a single step, or using a minimal number of steps, such that manufacturing costs per unit connector are reduced.
It would be still another advancement in the art to provide connectors that have a penetrating tip that provides improved cutting and insertion through an insulating layer in order to minimize the backflow of concrete through the resulting hole, particularly in the absence of pre-drilled holes.
It would be yet another advancement in the art if such connectors were also highly insulative.
Such connectors for facilitating the manufacture of composite wall structures incorporating reinforcement structures embedded within the structural layers are disclosed and claimed herein.